TRAGEDY: A cop speaks with workers yesterday outside the Yale building where the body of Annie Le was found. Meanwhile, a wedding gift arrived at her fiancé's house on Long Island. Photo: AP

Grim-faced authorities last night said they found a body believed to be that of Yale grad student Annie Le stuffed in a wall at the school lab where she vanished last week — and they hinted that a student may have failed a polygraph in the case.

“Shortly after 5 p.m., Connecticut State Police located the remains of a human secreted in a wall inside [the] building,” said New Haven Police Assistant Chief Peter Reichard.

Le, 24, was to have been married yesterday to a Columbia University grad student from Long Island.

Reichard also suggested that a student may have failed a lie-detector test when questioned about Le, but refused to provide details.

A young man was seen being led from the building for questioning early Saturday.

Asked whether a student had failed a polygraph, Reichard said only, “We can’t release any more information at this time.”

Le’s numbed family could barely speak.

“I’m sorry,” her aunt mumbled, still in shock.

Yale University President Richard Levin sent out a campuswide e-mail under the heading “Tragic News.”

“Our hearts go out to the family of Annie Le, to her fiancé and to her friends,” Levin said in a statement. “The family, the fiancé and the friends now must suffer the additional ordeal of waiting for the body to be positively identified.”

Sources had said police found bloodstained clothes stashed above a drop ceiling in the Yale lab over the weekend.

It was unclear whether the items were Le’s or her killer’s. It was reported that law-enforcement sources said the clothes were not the ones Le was seen wearing Tuesday as she passed a security camera while entering the building.

Earlier yesterday, authorities scoured a trash dump at a Hartford incineration plant where refuse from the lab is occasionally taken.

“They asked if they could come in and work around, and we did everything to accommodate them,” said Paul Nonnenmacher, a spokesman for the Connecticut Resources Recovery Authority, which runs the plant.

Reichard told the New Haven Independent that the search was “routine.”

At the Yale lab, authorities also hauled off refuse under tight security from two nearby Dumpsters.

Le, a pharmacology and molecular-medicine student, had been set to marry Columbia physics grad student Jonathan Widawsky at the North Ritz Club in Syosset.

At the off-campus house Le shared with other Yale students, a housemate who asked not to be identified recalled seeing her as she left Tuesday morning.

“I told her, ‘If I don’t see you before Sunday, congratulations and good luck,’ ” the woman said.